Method and system for parallactically synced acquisition of images about common target

ABSTRACT

A method and system are provided for parallactically synced acquisition of images about a common target from mutually displaced imaging positions. At least first and second imaging devices are disposed respectively at first and second imaging positions. The first imaging device is actuated to acquire a first image with a target of interest disposed at a predetermined relative position within a field of view thereof. The second imaging device is actuated to acquire a second image with the target of interest disposed within a field of view thereof. A target feature finder is executed in a processer to detect the target of interest within the second image. A plurality of user prompts are generated at the second imaging device responsive to detection of the target of interest in the second image. The user prompts include: visual indicia adaptively applied to the second image to visually distinguish the target of interest, and orientation correction alerts adaptively generated to guide angular displacement of the second imaging device to situate the target of interest at the predetermined relative position within its field of view.

RELATED APPLICATION DATA

This Application is based on U.S. patent application Ser. No.14/218,573, filed 18 Mar. 2014, which is based on Provisional PatentApplication No. 61/802,110, filed 15 Mar. 2013.

BACKGROUND OF THE INVENTION

The present invention is directed to a method and system which employpersonal communications devices known in the art such as smartphones,personal digital assistant (PDA) type devices, tablet computers, and thelike suitably equipped with built-in camera or other imagingcapabilities. Personal communications devices are employed at multipleviewing positions for various collaborative applications to reliablyacquire and/or track one or more common targets. The visual informationobtained through images acquired by each device may be integrated withthe device's inertial measurement information to augment the accuracy ofpositioning and/or tracking capabilities using the device.

The subject method and system improve upon various multiple sightingdevice systems and methods heretofore known, such as those disclosed inU.S. Pat. No. 7,225,548. In certain applications, the subject method andsystem enable multiple physically separated users to bring their imagecapture devices to bear on the same target. For example, the method andsystem enable various mobile personal communication devices to performrelative alignment functions using their internal cameras.

In accordance with certain aspects of the present invention, the subjectsystem incorporates the smartphone, tablet, PDA, or other suitablyequipped personal communications device of different users locatedwithin a proximate distance of one another. It may be desirable for oneuser to point out a vehicle, a bird in a tree, a person in a crowd, asign, or a landscape feature of interest using the device withoutresorting to descriptive discussion. Each user may dynamically pointfeatures out to the other by suitable selection on the image displayedon his/her device. Similarly, a collection of users may all follow thelead of a first user. Such operations would be beneficial for use invarious applications like military and law-enforcement, security, naturewatching, scientific observation. They may also be beneficial, forexample, in the context of augmenting social media to enable individualsto point out interesting things to their friends over a distance.

In other exemplary applications, the subject system may be used for timedelayed finding of market targets in the 3D world. For example, a user,having established a virtual reference point in the physical word mayrecord that information so that upon a revisit to the same general areathey may spot the point and find it again easily. Accordingly, thesystem may be used to mark points of interest for oneself or for others.A camera view of the world on one's smartphone or tablet may inreal-time combine available geo-location and orientation sensor datawith the pixel level processing according to the process of informationfusion described herein, to float visual markers or labels in the cameraview as if they were attached to the physical world being observed.Thus, any user may view both the real world and a virtual overlay in aspatially convergent user interface. Such overlays have furtherpotential in wearable computing solutions, such as electronic glasses,which obviate the need for the user hold up and point their computingdevice before them while walking.

Geo-tagged image or video transfer is an automatic function of many PDAtype or other such personal communications devices, yet theircorresponding tolerances tend to be wholly inadequate for meeting theneeds of tactical teams or others requiring finer precision. Forinstance, GPS chipsets (when operational) provide accuracy at best on ascale of tens of meters, while compass modules (when present andsufficiently distant from interference) provide perhaps 5-10 degrees oforientation accuracy. In GPS-denied and metal-heavy militaryenvironments, accuracies suffer even more significantly.

Thus, built-in functions of currently existing mobile devices forpersonal communications are not sufficient to bring multiple cameras tobear on the same target with the accuracy and reliability in manyapplications, especially if a “slew-to-cue” capability or accuratetactical position details on an observed subject of interest are to beprovided.

There is therefore a need for a method and system whereby personalcommunications devices at multiple imaging positions are coordinated toaccurately and reliably bring their imaging fields of view upon a commontarget. There is a need, moreover, for such method and system to provideprecise relative alignments between users' local points of view andprovide reliable image-based device orientation information relative tothe target for corrective integration with device IMU and related sensorpackage measurements. “IMU” is used contextually herein to describe anycombination of sensors or sensor packages that may track orientation andchanges in orientation, and, in certain embodiments, position andchanges in position, including but not limited to accelerometers,angular accelerometers, gyroscopic measurements, compass heading,inclinometers, GPS, differential GPS, RF ranging, and so forth.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method and systemfor accurately and reliably coordinating personal communications devicesat multiple imaging positions to align their fields of view with acommon target.

It is another object of the present invention to provide a method andsystem for automatically guiding image-based collaborative orientationof personal communications devices at multiple imaging positions withrespect to one or more common targets.

It is yet another object of the present invention to provide a methodand system that calibrates a personal communication device's availableIMU measurements by corrective integration with image informationacquired by the device.

These and other objects are attained by a method provided in accordancewith certain embodiments of the present invention for parallacticallysynced acquisition of images about a common target from mutuallydisplaced imaging positions. The method comprises establishing at leastfirst and second imaging devices respectively at a first and a second ofthe imaging positions. The first imaging device is actuated to acquire afirst image with a target of interest disposed at a predeterminedrelative position within a field of view thereof. The second imagingdevice is actuated to acquire a second image with the target of interestdisposed within a field of view thereof. A target feature finder isexecuted in a processer to detect the target of interest within thesecond image. A plurality of user prompts are generated at the secondimaging device responsive to detection of the target of interest in thesecond image. The user prompts include: visual indicia adaptivelyapplied to the second image to visually distinguish the target ofinterest, and orientation correction alerts adaptively generated toguide angular displacement of the second imaging device to situate thetarget of interest at the predetermined relative position within itsfield of view.

A method established in accordance with certain other embodiments of thepresent invention provides for automatically guiding visual alignment tomaintain coincident fields of view about a common target for imagescaptured from mutually displaced imaging positions. The method comprisesestablishing at least first and second image capture devicesrespectively at first and second imaging positions, and actuating thefirst image capture device to capture a first image with a target ofinterest substantially centered within a field of view thereof. Targetof interest and angular orientation measurement data of the first imagecapture device are transmitted to the second image capture device forguiding its angular orientation toward the target of interest basedthereon. The second image capture device is actuated to capture a secondimage with the target of interest disposed within a field of viewthereof. An angular orientation measurement for each of the first andsecond image capture devices is actuated when the first and secondimages are respectively captured thereby. A target feature finder isexecuted in a processer to detect the target of interest within thesecond image. A plurality of user prompts are adaptively generated atthe second image capture device responsive to detection of the target ofinterest in the second image. Such user prompts include: predefinedvisual indicia to identify the target of interest, and orientationcorrection alerts to guide angular orientation of the second imagecapture device to situate the target of interest substantially centeredwithin the field of view thereof. The orientation correction alertsinclude visually displayed directional markers applied to the secondimage.

A system formed in accordance with certain other embodiments of thepresent invention provides for parallactically synced acquisition ofimages about a common target from mutually displaced imaging positions.The system comprises at least first and second imaging devices disposedin displaceable manner at respective first and second imaging positions.The first imaging device acquires a first image with a target ofinterest disposed at a predetermined relative position within a field ofview thereof, and the second imaging device acquires a second image withthe target of interest disposed within a field of view thereof. A targetfeature finder module detects the target of interest within at least thesecond image. An integration module coupled to the target feature findermodule generates a plurality of user prompts at the second imagingdevice responsive to detection of the target of interest in the secondimage. The user prompts include: visual indicia adaptively applied tothe second image to visually distinguish the target of interest, andorientation correction alerts adaptively generated to guide angulardisplacement of the second imaging device to situate the target ofinterest at the predetermined relative position within the field of viewthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustrative image schematically illustrating the relativepositioning of mutually displaced imaging devices with respect to atarget of interest during use of an exemplary embodiment of the presentinvention;

FIG. 2 is a schematic diagram illustrating the interaction of certaindevices and components in a system formed in accordance with anexemplary embodiment of the present invention;

FIG. 3 is a set of images as acquired and displayed respectively at aplurality of mutually displaced imaging devices during use of a systemformed in accordance with an exemplary embodiment of the presentinvention;

FIG. 4 is a schematic diagram illustrating the interaction of certainmodules in a system formed in accordance with an exemplary embodiment ofthe present invention;

FIG. 5A is a comparative set of images as acquired and displayedrespectively at a plurality of mutually displaced imaging devices duringuse of a system formed in accordance with an exemplary embodiment of thepresent invention;

FIG. 5B is a schematic diagram geometrically illustrating the relativepositioning of mutually displaced imaging devices with respect to atarget of interest;

FIG. 6 is an illustrative graphic plot showing a sampling of points toindicate reliably high success rate for a target feature finding processexecuted by a system formed in accordance with an exemplary embodimentof the present invention;

FIG. 7 is a flow chart illustrating a flow of processes for set-up of animaging device employed in of a system formed in accordance with anexemplary embodiment of the present invention;

FIG. 8 is a flow chart illustrating a flow of processes for aninter-user ranging process carried out by a system formed in accordancewith an exemplary embodiment of the present invention;

FIG. 9 is a flow chart illustrating a flow of processes for a targetselection process carried out by a system formed in accordance with anexemplary embodiment of the present invention;

FIG. 10 is a flow chart illustrating a flow of processes for a targettracking process carried out by a system formed in accordance with anexemplary embodiment of the present invention;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Generally, the subject method and system automatically guide theparallactically synced acquisition of images, and preferably tracking,about a common target by imaging devices located at mutually displacedimaging positions. In an exemplary embodiment of the present invention,the subject method and system employ personal communications deviceswith built-in camera capabilities and user displays of their acquiredimages. For example, a system implementation employs handheld cameraenabled smartphones for various collaborative applications to reliablyacquire and/or track one or more common targets. In certainapplications, the system utilizes an energy reference frame to determinea baseline distance between two smart phone devices. A time of flightfor blue-tooth or ultrasonic signals are preferably used in thoseapplications. It further enables feature matching between imagingsystems using computer-vision derived image feature-matching technology,examples of which include suitable feature matching transforms known inthe art such as Scale Invariant Feature Transforms (SIFT), Speeded UpRobust Features (SURF), or any other simplified fast correlation ofimage components to find matched feature sets in images of each camera.A baseline distance between different users' devices is then used tocompute a relative angle so that one user may direct the other. Oncetargets have been acquired by each of the respective users' devices,built in or supplemental internal inertial measurement unit (IMU)capabilities for each device are preferably applied to track anidentified target (that is, update the device's orientation to maintainview of the identified target). Because a device's IMU will typicallydrift, repeated recalibration via matched imaging contributessignificant advantages over conventional systems which rely solely uponIMUs or, alternatively, GPS geo-locations (since standalone GPSpositioning is too imprecise to solve the problem of calculating localrelative angles for many applications).

The subject method and system may be applied in various fields for awide array of different applications. For instance, the subject methodand system may be used to enable one user to guide another user to focuson a particular person or target of interest. Additionally, the subjectmethod and system may be utilized to provide more precise geo-locationinformation about a particular target of interest. Such capabilities areadvantageous in a wide array of different operations including tacticaldismounted operations, forward observer or gunnery operations, andsecurity and policing actions, to name a few.

Another advantage of the subject method and system which bring multiplecameras from multiple positions to focus on the same target is theability to extract three dimensional (3D) point cloud information incertain applications. This allows for not only improved triangulation oflocations for purposes such as targeting, but may be adapted to enableback-end servers to construct a 3D mesh model in a more cost efficientmanner compared to currently available systems like Flash-LIDAR withoutsacrificing detail quality. In various tactical applications, thesubject method and system integrate handheld and mounted cameras toprovide real-time, evolving, 3D tactical maps to command personnel andto individual soldiers via their PDA type interfaces.

FIG. 1 illustrates use of a system formed in accordance with anexemplary embodiment of the present inventions. In the scenarioillustrated, two physically separated observers, each equipped with apersonal communications device, are looking for a target of interest 30,a particular vehicle in this illustration. This scenario is provided forillustrative purposes only and is but one of a host of differentsituations which would benefit from use of the subject system. In FIG.1, the two physically separated observers search for the target vehicle30. Once Observer 1 has spotted the target 30, the target is flagged asa reference by the system which captures both relative orientationinformation and image feature details therefor. Observer 2 preferablyreceives on his or her personal communications device guidanceinformation based upon the flagged reference. If target 30 is within thevisual field of Observer 2, the target is marked as such in his/herdevice's image by visual indicia, such as a target frame 32 (shown inFIG. 3). If the device must be moved to bring the target into view (orto center it within the view), a guidance arrow 34 indicates directionof the required device slew (shown in FIG. 3) toward that end.

The distance between observers and the target 30 in this example aresuch that the relative sight angle for each observer is significantlydifferent. GPS estimates of the observers' locations are not on theirown accurate enough to provide a baseline correction for the resultingparallax effect. Compass/IMU errors further conspire to make tracking tothe common target crude at best. The subject system utilizes acombination of processes to gracefully correct these inaccuracies and toprovide precise relative angle information to guide each device's user.The system allows multiple camera-equipped systems (handheld or mounted)to rapidly identify and slew to the same target. Once flagged, targetsand threats may also be tracked by the system and thereafter easilyrelocated by users (who may be fellow squad members engaged in tacticaloperations, for example).

FIG. 2 illustrates the general configuration of an orientation trackingsystem 20 formed in accordance with an exemplary embodiment of thepresent invention. System 20 includes amongst its features two or morepersonal communications devices 22 a, 22 b (such as the commerciallyavailable iOS line of devices). FIG. 2 illustrates the iOS devices 22 a,22 b being linked via a host 24 (comprising a Wi-Fi hub in the exampleshown) to a storage device 26 that may include a back end server,desktop, laptop computer, or the like. But the devices 22 a, 22 b may belinked in any other suitable manner known in the art forintercommunication and storage of information. Real-time processingoccurs locally on the iOS devices 22 a, 22 b; however, the host 24(implemented as a Wi-Fi hub in FIG. 2) preferably provides back-endservices to both host the devices' collaboration and to at leastpartially offload image and signal processing that might otherwise provetoo slow if entirely executed locally on the devices 22 a, 22 bthemselves. The collaboration between devices may also be accommodatedover a Bluetooth peer-to-peer network employed the host 24. However,Wi-Fi provides more practical communications range for manyapplications.

FIG. 3 illustrates screen shots from an embodiment of system 20employing a group of commercially available iPod devices to acquireimages configured for target tracking. In the top frame, a target 30appearing in an image acquired by a first device is identified andestablished as a reference. The reference is transmitted to another iPodor other iOS device 22 within the given group of devices. Each iPod 22tracks device orientation to the established target of interest 30,indicating with guidance arrows 34 which direction to slew the device 22to re-center its field of view on the same target of interest 30.

The bottom frame of FIG. 3 shows an image-based “feature find” operationon a second iPod, referenced to the first. In addition to the guidancearrows 34, a target frame 32 has been placed around the target sign 30.Tests suggest that targets may be located based on visual clues withgreater than 20 degrees of angular separation between observers.

The system 20 may be equipped with additional features such as attitudeindicators, inter-PDA messaging, and the ability to find range betweendevices to suit the particular requirements of the intended application.The user interface of system 20 incorporates, for example, numeroustouch-screen enabled properties like swipes to hide or access features,and automatic rotational adjustment of display orientation.

FIG. 4 illustrates the integration of information to provide updatedtracking information for a target 30 relative to a local user's personalcommunications device view. Unit items shown in blocks 40 and 42 providethe primary informational references in this configuration of thesystem: namely, a high-drift, low accuracy IMU 42, and an imageprocessing based target feature finder 40. When available, these unitsare supplemented by the features shown in blocks 50, 52 and 54: namely,GPS 52 and Compass 54 devices which provide coarse grained estimationsof absolute geo-reference frame information. Energy frame references 50provide information from point-to-point energy transmissions between theusers' personal communications devices, such as angle of incidence ortime-of-flight information, from which relative position data may bederived. An example is the exchange of ultrasonic cue signaltransmissions between personal communications devices. Items in blocks60 and 62 represent features which may be incorporated into the subjectsystem 20 depending upon the particularly intended application. Forinstance, frame-to-frame video comparisons 60 enable a user to trackfield motion and to integrate frames between devices to estimate 3Ddetails, and available external data 62 may enable integration withother systems.

In connections with target tracking which integrates data provided forinstance by a device's IMU and its target feature finder, theintegration problem is addressed by assigning time-varying confidencevalues to each data element. This creates an estimation problem that isrelated to Kalman tracking. The target feature finder has high,instantaneous confidence and provides the dominant correction to theother data.

The illustrated system 20 preferably employ a comparison algorithmoptimized for camera view angle, color and light balance, and otheraspects of the given iOS devices' cameras. Feature matching may beaccomplished by any suitable processes known in the art including butnot limited to SIFT or similar SURF. However, it is noted that SIFT andSURF feature vector computations are typically not fast enough forreal-time thin client applications. Furthermore, typical visual featuresmatching algorithms present significant limitations in the context oflarge displacements of the point-of-view.

Accordingly, system 20 utilizes a transform that producescomputationally fast results and has high accuracy in solving themultiple angle-of-view problem. FIG. 5A shows comparative imagesacquired by personal communications devices at mutually displacedimaging positions. They illustrate matching and recovery of a targetobject 30 from significantly different viewpoints. FIG. 5B schematicallyillustrates the parallax effect of such mutually offset devices 22 a, 22b with respect to a common target 30.

In FIG. 5A, each pair of frames shows a target 30 flagged on the left bytarget frame 32 a and the corresponding target automatically located inan image from another viewpoint flagged by target frame 32 b. As FIG. 5Aillustrates, the feature-matching processing executed by the systemoperates correctly notwithstanding significant differences in viewingangle between imaging devices and significant rearrangement ofextraneous foreground and background features as a result. Directionalarrows 36 are shown only for notational purposes, and not part of thevisually displayed indicia actually applied to an acquired image in theillustrated system embodiment.

The feature comparison process employed in the target feature findermodule of system 20 is based conceptually on SIFT processes known in theart. Comparisons may also be drawn to various alternative imageprocessing techniques, including but not limited to SURF, and variousauto- or cross-correlation image matching techniques.

Generally, in known conventional SIFT processes, transform features areextracted in four steps. The first step is to detect extrema in aderived scale space of the image. To do so, in a basic algorithm, theoriginal image is progressively blurred by convolution with a twodimensional (2-D) Gaussian function of increasing sigma, then aDifference of Gaussians (DoG) is created for each sequential pair ofsuch convolutions by subtracting from each blurred image thecorresponding blurred image with the next largest sigma. This process isgenerally implemented by blurring the image and down-sampling by powersof two (“octaves”), each of which is operated on over a predeterminednumber of sub-octave steps. This produces a set of two dimensional x-yreferenced matrices, DoG_(k), indexed by scale (k). Within this DoGspace one determines local minima or maxima points (i.e., extrema)relative to all neighbors in x and y pixel location dimensions and the kscale dimension. In typical implementation, the location of the featureis further refined down to sub-pixel accuracy using a truncated Taylorexpansion (up to, for example, the quadratic terms). Extrema featurepoints are eliminated if they have low contrast (and thus exhibit poorsensitivity), or if they fall on an edge (and are thus poorlylocalized). The third step of conventional SIFT is to assign anorientation to each feature based upon local image gradients at a givenlocation. The direction of the largest gradient is generally the primaryorientation associated with the feature point, though features pointsmay be duplicated if there are additional gradient directions at least80% as strong as the largest gradient. This is a course-grainedoverview; however, mathematical details, other considerations andrelated process variants are well understood in the art. Once thisinformation has been computed, the final step is to calculate thefeature descriptor vector.

Feature descriptor vectors are calculated using local gradients in anarea around a feature point and are typically computed in an oriented,multi-dimensional histogram grid around the feature point, taken withreference to its preferred scale and primary orientation. This providesa signature vector that is useful for matching features from one imageto features from another. To perform object recognition, the SIFToperation is performed on both the reference image and a test image, andonly those features which match with respect to their signature vectorsare used. Clusters are formed by sets of features, the co-occurrence ofwhich, with the same relative orientation, scale, and pose (ordisposition relative to each other across space), provides highconfidence that an object in any image or set of images is the sameobject each time said clusters are found. Clusters of features arepreferably employed over individual feature points in matching toeliminate spurious matches. An object is considered to be successfullyidentified if there are a certain number of features—for example, atleast 3 features—are found in the final cluster.

While full conventional SIFT, or SURF (a related multi-scale waveletbased analysis) may be employed to match images, it is cumbersome to doso in real-time due to hardware speed limitations in practical systemsof interest. Thus, in accordance with certain aspects of the invention,system 20 in the illustrated embodiment executes a reduced matchingprocess which, when taken together with appropriately set thresholds forsuccessful matching, increases the speed of image feature matching.Moreover, the speed of image feature matching, whether full or reduced,may be increased by wholesale relocation of SIFT/SURF or relatedprocesses from the mobile imaging devices themselves to a supportingserver or other processor resource, or by carrying out the mostprocessing-intensive portions offboard and supplementing the same withless burdensome portions carried out locally onboard the devices,depending on the particular requirements of the intended application.

In accordance with an exemplary embodiment of the present invention, thereduced matching process carried out by system 20 for target featurefinding includes computing the Difference of Gaussians (DoG) for alimited number of scales for the reference and test images. Thesereference and test images will correspond, for example, to the leaduser's target image and secondary user's full FOV image. Rather thanreducing to extrema-point feature keys, the illustrated embodimentrelies on certain characteristics specific to the cooperativesight-picture target finding application to simplify processing. Inparticular, physical targets will typically remain upright as will thelead and secondary users. Moreover, though to a lesser extent, thephysical target will typically have a similar size in the visual fieldunless the users are at greatly different range to the target. Thus, theapproximate target upright relative orientation and scale constancybetween the lead and secondary users' acquired images will yieldconstancy in the local shape of their respective DoGs around the target,which in turn, allows a fast cross-correlation to be exploited betweenthe reference image's DoG and the test image's DoG. For speed, thiscorrelation may be further limited to a predetermined set of scale andoctaves. An embodiment optimized to favor fast processing overcross-scale matching accuracy may, for example, employ only 2 Gaussiansevenly spaced in only the first octave. With DoGs thus produced for boththe reference and test images, the maximum cross correlation shift ofthe two is subsequently determined and used to find the location withinthe test image most likely to contain the reference object of interest.It is therefore the collapsed DoG space that is operated on in themanner of finding peak correlation.

On account of contrast and lighting variations across the field that mayotherwise artificially dominate the peak finding, the summation valuemust be normalized to make a robust decision. Such normalization may beaccomplished in two stages: first, subtracting the average pixel valueof the reference image DoG from both DoGs and calculating thenormalization coefficients for each pixel and second, then dividing thesummation by these coefficients at each pixel to obtain a normalizedsummation arranged so that a perfect match will have a value of one.These normalization coefficients are determined by calculating acorrelation between: a matrix of the squares of each pixel of thede-meaned test DoG, and a matrix of the same size as the reference imageDoG but containing only unit values. Thereafter, the pointwise squareroot at every pixel location is taken and multiplied by the square rootof the sum of the squares of the pixels in the reference image DoG.

Peaks above a predetermined threshold in this normalized space are foundin order to produce a list of candidate locations for the referenceimage features within the test image. The final determination of a bestmatch is made in accordance with predetermined rules. In certainalternate embodiments, further analysis may be done on each of thesecandidate locations to identify a preferred match. Generally, thelargest peak is simply chosen and compared to a preset threshold todetermine whether or not to accept the result provided. Thus, in asystem formed in accordance with an exemplary embodiment of the subjectsystem, a lead-user's target image is matched to a location in thesecondary user's FOV image or is rejected as not findable in that FOV ifno match exceeds the predetermined value.

Again, where, in a particular application, a smartphone with limitedprocessing speed such as the iPhone is used as the personalcommunications device and no accelerator or linked server processing isavailable, some of the aspects of the target feature finding process aresimplified. To summarize: first, the Difference of Gaussians (DoG) aswith SIFT is computed and then the cross-correlation between thereference image's DoG and the test image's DoG is determined. Thiscorrelation is added together for every scale and every octave. Topreserve for processing speed, it may be desirable to use 2 Gaussiansevenly spaced in only the first octave. Next, the maximum value of thesummation is determined and normalized and used to define the locationmost likely to contain the object of interest.

To normalize the summation, the average pixel value of the reference DoGis subtracted from both DoGs and normalization coefficient for eachpixel is computed. The summation is then divided by the coefficients ateach pixel to obtain a normalized summation where a perfect match willhave a value of one. The normalization coefficients are computed bygenerating a correlation between a matrix of the squares of each pixelof the determined test DoG and a matrix of the same size as thereference DoG containing only ones. Then, the square root of every pixelis multiplied with the square root of the sum of the squares of thepixels in the reference DoG. A threshold is thereby set to definewhether or not to accept the result provided.

Processing in this manner is advantageous in that it allows a user toset a threshold of confidence in the findings. Hence, when the processfails to find the correct match—either because the target is not withinthe field of view or the processing is confused by other visualfeatures—the location estimate may be ignored.

To illustrate utility of the simplified processing, FIG. 6 shows asample ROC (“receiver operator characteristic”) curve generated byvarying such threshold over a representative set of target findoperations carried out by system 20 in an illustrative application. Asis well understood in the art, this curve displays measurements of thetrade-off between true-positive accurate detections and false-positiveincorrect detections as one adjusts variables such as a detectionthreshold. The ROC curve indicates that a user's device is reliably ableto flag and reject bad matches of the target reference image within testimages. Moreover, since each video frame captured by a device may besearched to locate the reference target, the density of reliable targethits available for tracking is significant even if matches to the targetin many frames are rejected as unreliable.

In addition to the IMU and feature-based corrections, the subjecttracking system preferably uses ultrasonic ranging between devices andderives a parallax baseline estimate therefrom. This estimate isobtained by emitting a timed chirp at each personal communicationsdevice 22 a, 22 b in response to a query from either user. Each devicereceives the other's chirp, and a time of flight is calculated. Thisrenormalizes the range between devices. While described in connectionwith two users, the estimate may also be achieved when greater numbersof users are involved in tracking. In such instances, each user's devicepreferably receives the chirp from the remaining users.

In accordance with certain aspects of the present invention, the subjectsystem incorporates the smartphone, tablet, PDA, or other suitablyequipped personal communications device of different users locatedwithin a proximate distance of one another. It may be desirable for oneuser to point out a vehicle, a bird in a tree, a person in a crowd, asign, or a landscape feature of interest using the device withoutresorting to descriptive discussion. Each user may dynamically pointfeatures out to the other by suitable selection on the image displayedon his/her device. Similarly, a collection of users may all follow thelead of a first user. Such operations would be beneficial for use invarious applications like military and law-enforcement, security, naturewatching, scientific observation. They may also be beneficial, forexample, in the context of augmenting social media to enable individualsto point out interesting things to their friends over a distance.

In other exemplary applications, the subject system may used for timedelayed finding of market targets in the 3D world. For example, a user,having established a virtual reference point in the physical word mayrecord that information so that upon a revisit to the same general areathey may spot the point and find it again easily. Accordingly, thesystem may be used to mark points of interest for oneself or for others.A camera view of the world on one's smartphone or tablet may inreal-time combine available geo-location and orientation sensor datawith the pixel level processing according to the process of informationfusion described herein, to float visual markers or labels in the cameraview as if they were attached to the physical world being observed.Thus, any user may view both the real world and a virtual overlay in aspatially convergent user interface. Such overlays have furtherpotential in wearable computing solutions, such as electronic glasses,which obviate the need for the user hold up and point their computingdevice before them while walking.

In accordance with an exemplary embodiment of the present invention,set-up of the subject system is accomplished by carrying out the stepsillustrated in FIG. 7. Preferably, users activate respective device appssuitably implemented in their personal communications devices. Then,each device begins collecting video frames and displaying them. Finally,each device's absolute compass heading and angle of elevation isestimated from its IMU data, and a baseline point is recorded.

More specifically, as shown in block 701, each device provides the usera view and also initiates its camera to begin collecting video framesupdated on a quasi-real time basis. In certain exemplary embodiments,the user is afforded a view directly through the camera, as is typicalof smartphones, tablets, PDAs and other personal communications devices,by providing a real-time display of the camera view on the screen. Inalternate embodiments, the camera may operate in parallel to an opticalor other secondary view system. Such an alternative would beappropriate, for instance, where the device is used in conjunction withmagnifying optics, for example, a scope or binoculars, or in a wearablecomputing configuration where the user's view is directly throughaugmented glasses or similarly linked viewing equipment.

In block 702, each device sets up and determines its baselineorientation according to available IMU data. In many devices thisincludes magnetic compass azimuth and angle of elevation determined byaccelerometers. In such embodiments, a convenient, absolute orientationis available. However, this is an optional feature which may beincorporated in certain embodiments of the system. In other embodiments,a baseline orientation point is recorded by the system against whichfuture orientation changes are measured.

An IMU is used herein to describe any combination of sensor packagesthat may track orientation and changes in orientation, and, in certainembodiments, position and changes in position. As is well understood inthe art, accelerometers and rotational accelerometers of a variety oftechnologies may be used to achieve this goal. These may be combinedwith, for example, a flux gate or other electronic compass, GPS, etc.(see FIG. 4) to achieve better absolute referencing. Again, it is notedthat in accordance with certain aspects of the present invention, issuesof accuracy, variance, and drift in these various sensor packages areovercome to achieve a level of co-alignment on a target that would nototherwise be possible, particularly in small, commodity priced devices.

In accordance with an exemplary embodiment of the present invention, thesubject system carries out inter-user ranging according to the processas illustrated in FIG. 8. Generally, range calibration is selectivelyinitiated by a user pushing a button or, alternatively, the system maybe programmed to initiate at predetermined intervals. Next, each deviceemits a chirp, one delayed from the other. The devices listen for oneanother's chirps. Thereafter, the times of the chirps are compared to anotice event signal sent by the RF network, and the times of flight arecomputed and averaged for the chirps to obtain inter-user baselinedistances.

As previously discussed herein, it is desirable to measure a base linedistance or positional offset between the two or more user devicesinvolved in the cooperative imaging process. Absolute references such asGPS provide bearing information, but, on their own, yield insufficientaccuracy for the purpose of making necessary parallax angle corrections.Thus, it is preferable to supplement such coarse measurements or users'estimates with an energy frame reference-based inter-user ranging. Thismay be achieved by numerous means; however, in an exemplary embodiment,a sonic chirp transmitted between each pair of devices is used toimprove baseline distance estimates.

Referring to FIG. 8, in certain embodiments, a device orientationtracking process is automatically initiated while in other embodiments,the orientation process is manually initiated, as shown in block 801.Manual calibration is preferable when stealth operation is desired, asusers will typically have a good idea when they have moved away fromtheir last operation points. However, automatic initiation is easilyimplemented either at fixed intervals, or upon predetermined conditionswhich may include, for example, motion of one of the other units ofgreater than a predetermined amount, or a failure to find shared targetswithin a predetermined accuracy.

Upon initiation of the process, a cue is transmitted, as shown in block802, from the initiating device. This cue instructs the other devicesthat a baseline calibration is taking place, and in accordance withcertain embodiments also provides a time reference for time of flight(TOF) calculations to be performed at the end of the process. Thus thecue is preferably transmitted over an RF network link or other fastchannel between the devices, so that its time of propagation is not asignificant factor in these calculations. Any suitable means known inthe art for progressive call and response between units may be used inresolving inter-unit distances.

The devices preferably chirp in a predetermined order, as indicated inblocks 803 and 804. Preferably, the device initiating the cue goesfirst, with the second system following after a predetermined delay. Inother embodiments, fixed delays may be predetermined or random delaysgenerated on the spot. While this is illustrated for two devices, theprocess may be extended to any suitable number of devices by suitablysequencing chirps from additional devices. Delaying different devices'chirps is preferred to avoid cross interference between the sounds asthey propagate between devices, however, it is not a strict requirementso long as each device knows the time at which the other device's chirporiginated. Moreover, preferred embodiments include pulse coding of thechirps so that they have good auto-correlation properties for detectionat a tight time accuracy and good cross-correlation properties to avoidone chirp interfering with another should it (or an echo) overlap withanother device's chirp.

The term ‘chirp’ is used generically herein to describe any emittedsound or ultra-sound from the devices. However, a sound that exploitspulse-compression and other waveform shaping concepts well-known insonar, radar, and other ranging fields is preferred.

According to block 805, each device listens for the chirps of other(s)and upon detection, locates the chirp in time and compares that time ofarrival to the cue time (the time that the system initiated inter-userranging). After subtracting the known delay between the cue time and thetransmit time, each device may thus compute an inter-device TOF. Inaccordance with the physics of sound, it may compute from the TOF andspeed of sound the distance between devices as indicated in block 807.

Preferably, the distance is measured with chirps in both directions andwith multiple chirps with varied properties, so as to control formulti-path echoes and other variations that might throw off any singlemeasurement. Measurements are preferably cross thresholded, to determinewhich correspond to the shortest distances between devices, and thosethat are closest are averaged to determine a final estimate.

In accordance with an exemplary embodiment of the present invention, thesubject system carries out target selection by a process such asillustrated in FIG. 9. Generally, a first user centers cross hairs ofhis/her display on a target of interest and activates targeting. Then,the first user's device collects a photograph of the target using theregion around the crosshairs and computes the instantaneous orientationof the camera using IMU data. Next, the target image is transmitted to asecond system and/or server. The second user is directed to slew to theapproximate FOV, and a second image of the entire field is acquired fromthe second user's camera. Each of the images is preferably analyzed tocompute a two scale level difference of Gaussian (DoG) matrix,normalized by local brightness. Thereafter, the RMS cross correlation istaken between the target image DoG and the second image DoG, and thepeak is compared to a threshold to determine if the target is found inthe second image. If the target is found in the second image, then it isboxed or otherwise indicated visually in the second user's acquiredimage. The pixel offset from the second users cross hairs is calculated,as is an angle of offset from the present orientation of the userdevice.

Referring to FIG. 9, the first (or lead) user centers crosshairs on atarget of interest and marks this as a target. Marking of a target, asshown in block 901, is preferably achieved by means of a soft button onthe user's smartphone interface, but physical buttons, or gesture, eyeblink, or body-movement input may be suitably substituted in variousalternate embodiments. This activates a recording of data for the targetand a linked targeting process. The first user's device collects animage of the target in a predefined region around the crosshairs (block902), preferably smaller than the entire field of view (FOV) and in someembodiments, adjusted for range of the target. For speed, this istypically a square segment of the image but may be any otherpredetermined shape or irregular or edged-defined region.

Preferably, concurrent with image collection, the system also computesand stores the instantaneous camera resolution (block 903), inaccordance with the capabilities of the IMU/sensor package in thesmartphone as discussed herein. This information is used in computing arelative slew offset for the second user (or users.) Any suitable numberof users may potentially follow a single lead user who has set a target.Multiple users may quickly exchange roles between fixing targets as leador follow directions to targets as followers. Target information fromone or more users for multiple targets may be recorded simultaneously incertain embodiments. In other embodiments, the information may be storedin memory and recalled at later time. However, for simplicity ofexplanation an exemplary embodiment described herein focuses on a singleuser setting a target for the others to find. Steps similar to thoseillustrated for the single user setting/leading embodiment may beapplied to alternate embodiments involving multiple targets and multipletarget sources (leaders).

According to block 904, target information, including the orientationreference data and an image reference, is transmitted from the lead user(or other source) to the other devices involved in the orientationtracking. In accordance with an exemplary embodiment of the presentinvention, the system network is configured to include at least onesystem to set the target and at least one system to find the target.Generally, these systems are separate units held and operated by twoseparate users; however, in the case of delayed finding, a single unitmay be utilized for setting the target and subsequently locating thetarget. The network also includes a server unit with higher-processingcapability, which is configured to process data on behalf of thehand-held, smartphone client units, as illustrated in FIG. 2. Theprocessing capabilities and the manner by which computations aredetermined are not restricted to a specific configuration. Rather, thesystem may be configured in any manner suitable to provide a practicalsystem resource distribution that is able to work in real-time usingavailable hardware.

The result of calculations preferably include the target orientation ofthe lead device relative to a known reference point, the relativedisplacement of any given second unit from the first, and the relativerange of the target itself from the respective devices. Accordingly, inblock 905 each secondary (following) device is directed to adjust itsorientation so that its camera will be centered on the target ofinterest. Because errors and drift are normally anticipated, thepractical result of this direction is that a user should at least directthe secondary unit's camera so that the target of interest is within itscamera's field of view. Thus, the FOV provides a maximum bracket for theinitial calculations used to direct the secondary user to the target.

As previously discussed herein and illustrated in FIG. 3, numerousmeasures are available for guiding a user to the target; however, thepreferred mechanism for a handheld sighting unit is to provide visualorientation correction alerts like arrows disposed at the periphery ofthe camera image showing the necessary direction of orientation slew(adjustment).

According to block 906, in accordance with a preferred embodiment of thepresent invention, an image of the entire camera FOV is acquired oncethe secondary user is sufficiently oriented in the general direction ofthe target. This acquisition may be triggered automatically once the FOVis determined to overlap the target, or alternatively, may be triggeredmanually by touching a “find” button on the user interface screen. Themethod of triggering is variable depending upon the computing poweravailable in each specific application.

Next, according to block 907, the secondary image is analyzed to searchwithin it a match to the target reference image. Again, depending uponavailable hardware this operation may occur locally or may be undertakenby a network linked processing server. In certain embodiments, multipletargets or adjusted images will be queued and processed to enable theaggregation of information over time. For instance, as illustrated inFIG. 2, two or more pointing/imaging devices (each of which may take therole of lead or follower) communicate via a Wi-Fi network hub on whichis also configured a processing server. Each PDA style pointing deviceruns an application that permits users to visualize and interact withthe camera view, while the processing server is available for the rapidcomparison of images acquired at each respective unit. The PDA devicesare capable of performing the image comparisons locally. For moreseamless and nearly instantaneous tracking of target reaction times, itmay be desirable to utilize a processing server for image comparisonsrather than performing the comparisons locally. Other PDA devices,tablets, or other pointing/imaging devices of others do not necessarilyrequire the third server component. In other embodiments, Bluetooth,edge, 3G, or LTE connections or the like may be used in place of Wi-Fi.

The basic operation of finding the refined target location is summarizedin decision block 908. As described in preceding paragraphs, the actualcomparison in the illustrated embodiment is carried out as follows:

Each image (the target and the secondary FOV capture) is analyzed tocompute a multi-scale “difference of Gaussian” (DoG) matrix. For speed,and depending on the pixel resolution and processing hardware, as twolevels may be used to form a single matrix. A DoG operation comprisesfinding the convolution of an image or image segment with a first 2DGaussian function, finding the convolution of the same image or imagesegment of a second 2D Gaussian function of different scale than thefirst, and then subtracting one convolution matrix from the other. Suchfunctions form the basis of SIFT (Scale Invariant Feature Transform) andother image processing operations. The execution of these operations maybe rearranged mathematically to achieve the same result in morecomputationally efficient manner than is achieved by performing theseoperations individually. Moreover, functions other than a Gaussian, suchas for example, a compact wavelet, may be exploited in place ofGuassians. Thus, there are numerous substantially equivalentmathematical means to generate the DoG or a DoG type matrix which may beused in systems formed in accordance with alternative embodiments of thesubject invention. The DoG matrix is normalized by local brightness ineach image, in order to control for lighting angle variations.

Once a lead user acquires a target image, a secondary user acquires aFOV image oriented in a direction in accordance with the best availableestimate of the target's relative direction to the second usersaccording to IMU based calculations. This target image is transmittedalong with the FOV image user to a common processing platform.Typically, this is the second user's smartphone or a common sharedprocessing server but may be any other device which is able to receiveand process the transmitted image.

Each image is reduced to at least two Gaussian blurred renderings at twodistinct values of sigma, where sigma is a measure of the radialdiffusing effect of the 2-D Gaussian function. Each pair of Gaussianblurred renderings is subtracted to form a DoG. In minimum configurationthen, there are two blurred renderings: one DoG for the target image andone for the FOV image. Each DoG in the minimum configuration comprises a2-D matrix of value similar in size to the original image.

Each DoG is subsequently normalized in accordance with the processpreviously discussed herein and after normalization, a cross-correlationis performed between the normalized DoG matrices from the target and theFOV image. The peak of this cross-correlation is taken as the mostlikely candidate for where the target image is located within the FOVimage. If this value exceeds a threshold at this peak, a match isdeclared, otherwise no match is declared.

In the event that a match is declared, the region is boxed in thesecondary user's display by a target frame. Its pixel distance from thesecondary users' cross-hairs is converted to a vector angle ofdivergence from the center of the camera, and this angle is used toadjust the secondary user's IMU-based estimate of the targets relativeorientation so that the user will be guided to the correct target pointby the arrow feedback system with high precision.

Typically, the lead user's view of the target will differ from thesecondary user's view, due to rotation, parallax angle, and lightingangle. Thus, the goal of the image processing is not necessarily to findan identically matching image segment, as this is rarely possible.Instead, the goal of the image processing is to discover a constellationof features in the image which match but which may have moved slightlyrelative to each other. This concept is consistent with SIFT and SURFand other computer vision techniques known in the art.

To complete execution of the comparison in block 908, an RMScross-correlation is taken between the target image DoG and thesecondary FOV image DoG matricies. If the peak exceeds a predeterminedthreshold, that peak is considered a match for the target image and thepeak's location is treated as the location of the target within thesecondary FOV image. If the target is not found in a given round ofprocessing, the system continues to utilize the IMU based orientationcalculations to direct the secondary user to slew toward the target, asillustrated by the loop back from block 908 to block 905.

If the target is identified within the secondary user's FOV, thenaccording to block 909, the preferred system will draw an indicator boxaround that target in the video view pane in the secondary user's FOV.Preferably, once this box has been drawn, it is subsequently moved withthe image so as to remain over the target point as the user slews his orher sighting device. In addition, according to block 910, the pixeloffset from the FOV's center cross hairs to the target is computed, thusproviding an orientation correction to the system. The orientationfeedback arrows (or other suitable orientation correction alerts) willsubsequently respond to this finer-tuned location as their target.

The subject system is preferably equipped with sufficient measures tocontinually track targets via IMU corrections and cross-check the targetvia feature matching, thus providing a seamless, high resolution userexperience. Alternatively, the system may be modified such that afterperforming one round of target selection, subsequent operations areenabled only responsive to manual request by a user.

In accordance with an exemplary embodiment of the present invention, thesubject system carries out target tracking by a process such asillustrated in FIG. 10. Generally, once a target has been identified oneither system, each respective user has an orientation availablerelative to their internal IMU. At each update frame, the differencebetween present orientation and target orientation is computed and oneof four directional arrows are illuminated on the user's screen toindicate adjustments necessary to re-center the target.

More specifically, as shown in block 1001, the first step of targettracking is establishing a target. This may be accomplished by a singleuser marking a target, a lead user marking a target and sending thatinformation to the other users, by auto-marking of targets based on somepredetermined criteria, or by recalling a previously marked target fromstored memory. The target is presumed to be described by its orientation(elevation and azimuth) relative to a predetermined position, withadditional data preferably including an image or processed featurethereof. Additional absolute geo-location reference information may ormay not be included in the target data.

Subsequently, as shown in block 1002, the tracking device (which may bethat of the original leader or any secondary follower) computes thetarget's relative orientation according to the local device's currentIMU estimated orientation. Again, this may be estimated relative toabsolute references, such as compass heading and angle of elevationrelative to the earth, or estimated relative to a previously fixedorientation from which subsequent rotations have been tracked using theIMU. This forms the first estimate of the target's relative location. Itis further corrected according to the parallax angles (as described withreference to FIG. 9) so that any separation between the originaltargeting users and the following users, and the relative distances tothe target, are accounted for in computing the estimate orientation ofthe users' devices relative to the common target.

As illustrated in block 1003, and as described with reference to FIG. 9,if the target is estimated to be within the user's FOV, image featurefinding is applied to find the target features within the FOV. If it isfound, then this data is used to correct the IMU based target directionestimate, as described.

If additional data is available, such is also fused into improving thisestimate (block 1004). FIG. 4 provides some examples. In particular, GPSmay be used to check and update the user's position relative to theoriginal predetermined lead user position. As described in precedingparagraphs, acoustic chirps may provide an energy frame reference withwhich to update the baseline distance between two users. Any othersuitable energy frame reference known in the art, such as those based onlight ray angles, and the like may be used in certain alternateembodiments.

The use of the features disclosed in blocks 1002-1004 are optionaldepending upon the particular requirements of an intended application.In other words, systems formed in accordance with the present inventionmay include any combination of these features.

In block 1005, having arrived at a final best estimate of the target'sorientation relative to the current orientation of the user's sightingdevice, the user is thus directed to slew his or her sighting devicetoward the correct orientation. One approach for slewing toward thecorrect orientation has been previously described herein with referenceto FIG. 3.

Thereafter, the system optionally removes the slew direction guidancearrows 34 and presents other feedback to the user related to targetlocation. Specifically, once the system has located the target,crosshairs are highlighted as provided in block 1006. In accordance withan exemplary embodiment of the present invention the guidance arrows 34(as seen in FIG. 3), are removed and an identification circle 38 isflashed around the center target point when the pointer is within apredetermined number of degrees of exact visual coincidence with thetarget 30.

In the event that the system determines that the user is off-target, butthe target appears discernibly in the user's FOV, a visual tag may beplaced in the view field to mark the target (as shown in block 1007).Thus, in the example illustrated in FIG. 3, a target frame 32 hoversaround the identified target 30 in each of the FOV's shown while thetarget remains visible in that FOV.

In the simple case of a single target, this target frame 32 helps guidethe user to center their sighting device very quickly. In the case wherethe system is used to mark multiple targets, various informationalindicia, including but not limited to color coded markers, may begenerated to hover simultaneously around any and all targets ofinterest.

In accordance with FIG. 10, the tracking operation loop preferablycontinues (looping from block 1007 to block 1002) until manuallydiscontinued by the user or a new target of interest is established.Preferably, this loop is common to both the lead and secondary devicesonce a target is established. Thus, the leader's device will help leadits user back to the same target if they slew off target. This is incontrast to other embodiments which may track wherever the leader ispointing as the current target for each iteration.

In accordance with an exemplary embodiment of the present invention,where a match to the first user's target is not found in the seconduser's field of view during target selection, the subject system carriesout the process of IMU target information exchange. The absolute IMUbased orientation of the first users device is transmitted to the seconduser and the baseline distance between devices is used to determine aparallax angle. The second user's device is then directed toward theproper angle to intersect with the first user's view selected targetpoint. Thereafter, the camera focus or other suitably accommodatedmechanism is used to estimate the range of the target to enable precisecomputation. Alternatively, the system may be designed to apply anapproximate operating range which gives practical solutions for mostworking distances.

The system and method disclosed herein will have broad applicationapparent to those skilled in the art once they have understood thepresent disclosure. Upon reviewing the novel combinations of elementsdisclosed in the specification and figures and the teachings herein, itwill be clear to those skilled in the art that there are many ways inwhich the subject system and method may be implemented and applied. Thedescription herein relates to the preferred modes and exampleembodiments of the invention.

The descriptions herein are intended to illustrate possibleimplementations of the present invention and are not restrictive.Preferably, the disclosed method steps and system modules/units arewholly or partially programmably implemented in computer based systemsknown in the art having one or more suitable processors, memory/storage,user interface, and other components or accessories required by theparticular application intended. Suitable variations, additionalfeatures, and functions within the skill of the art are contemplated,including those due to advances in operational technology. Variousmodifications other than those mentioned herein may be resorted towithout departing from the spirit or scope of the invention. Variations,modifications and alternatives will become apparent to the skilledartisan upon review of this description.

That is, although this invention has been described in connection withspecific forms and embodiments thereof, it will be appreciated thatvarious modifications other than those discussed above may be resortedto without departing from the spirit or scope of the invention. Forexample, equivalent elements may be substituted for those specificallyshown and described, certain features may be used independently of otherfeatures, and in certain cases, particular combinations of method stepsmay be reversed or interposed, all without departing from the spirit orscope of the invention as defined in the appended claims.

What is claimed is:
 1. A method for parallactically synced acquisitionof images about a common target from mutually displaced imagingpositions, the method comprising: establishing at least first and secondimaging devices respectively at a first and a second of the imagingpositions; actuating said first imaging device to acquire a first imagewith a target of interest disposed at a predetermined relative positionwithin a field of view thereof; actuating an orientation sensor toacquire an instantaneous angular orientation measurement of the firstimaging device; transmitting the angular orientation measurement fromthe first imaging device to the second imaging device to thereby guidepreliminary angular adjustment of said second image capture devicetoward the target of interest; actuating said second imaging device toacquire a second image with the target of interest disposed within afield of view thereof; acquiring an angular orientation measurement ofthe second imaging device when the second image is acquired; executingin a processer a target feature finder to detect a location of thetarget of interest within the second image by comparatively processingimage features of the first and second images acquired by the first andsecond imaging devices; generating a plurality of user prompts at saidsecond imaging device responsive to detection of the location of thetarget of interest in the second image by the target feature finder tothereby further guide angular adjustment of said second imaging devicebased on the comparative processing of the image features, the userprompts including: visual indicia adaptively applied to the second imageto visually distinguish the target of interest, and orientationcorrection alerts adaptively generated to guide angular displacement ofsaid second imaging device to situate the target of interest at thepredetermined relative position within the field of view thereof;actuating a selected one of the first and second imaging devices toacquire at least one subsequent image; acquiring a subsequent angularorientation measurement of said selected imaging device relative to theknown reference point when the subsequent image is acquired; computingan orientation difference between the subsequent angular orientationmeasurement and an angular orientation measurement acquired for aprevious image acquired by said selected imaging device; and adaptivelygenerating subsequent orientation correction alerts responsive to theorientation difference computation to thereby guide subsequent angularadjustment of said selected imaging device to situate the target ofinterest at the predetermined relative position within the field of viewthereof.
 2. The method as recited in claim 1, wherein target of interestdata of said first imaging device is transmitted to said second imagingdevice, said second imaging device being guided to slew in angularorientation toward the target of interest based on the transmittedtarget of interest data and transmitted instantaneous angularorientation measurement.
 3. The method as recited in claim 1, whereinthe predetermined relative position for the target of interest iscentered within the field of view of an imaging device.
 4. The method asrecited in claim 1, further comprising inter-device ranging to measure abase line distance between said first and second imaging devices forparallax angle correction thereat with respect to the target ofinterest, said inter-device ranging including the exchange of at leastone cue signal between said first and second imaging devices, said cuesignal having a predetermined energy frame reference type.
 5. The methodas recited in claim 1, wherein the orientation correction alerts includevisually displayed directional markers applied to the second image. 6.The method as recited in claim 1, wherein said comparative processing ofthe first and second images by said target feature finder includesgenerating scale invariant feature transform (SIFT) image features forcomparative matching with the target of interest.
 7. The method asrecited in claim 1, wherein each of said first and second imagingdevices includes a personal communications device selected from thegroup of consisting of: smartphones, personal digital assistant devices,portable camera devices, and portable entertainment devices.
 8. Thesystem as recited in claim 1, wherein: the orientation correction alertsinclude visually displayed directional markers applied to the secondimage; and each of said first and second imaging devices includes apersonal communications device selected from the group of consisting of:smartphones, personal digital assistant devices, portable cameradevices, and portable entertainment devices.
 9. A method forparallactically synced acquisition of images about a common target frommutually displaced imaging positions, the method comprising:establishing at least first and second imaging devices respectively at afirst and a second of the imaging positions; actuating said firstimaging device to acquire a first image with a target of interestdisposed at a predetermined relative position within a field of viewthereof; actuating said second imaging device to acquire a second imagewith the target of interest disposed within a field of view thereof;executing in a processer a target feature finder to detect a location ofthe target of interest within the second image by comparativelyprocessing image features of the first and second images acquired by thefirst and second imaging devices; and generating a plurality of userprompts at said second imaging device responsive to detection of thelocation of the target of interest in the second image by the targetfeature finder, the user prompts including: visual indicia adaptivelyapplied to the second image to visually distinguish the target ofinterest, and orientation correction alerts adaptively generated toguide angular displacement of said second imaging device to situate thetarget of interest at the predetermined relative position within thefield of view thereof, wherein said comparative processing of the firstand second images by said target feature finder includes: generating areference Difference of Gaussian (DoG) for at least one portion of thesecond image and a target DoG for the target of interest,cross-correlating the reference and target DoG's for a predefined set ofcomputational scale spaces and octaves, summing the cross-correlationsgenerated for each of the computational scale spaces and octaves, anddetermining a maximum value of the summed cross-correlations torepresent the most likely image location for the target of interest. 10.A method for automatically guiding visual alignment to maintaincoincident fields of view about a common target for images captured frommutually displaced imaging positions, the method comprising:establishing at least first and second image capture devicesrespectively at first and second imaging positions; actuating said firstimage capture device to capture a first image with a target of interestsubstantially centered within a field of view thereof; transmittingtarget of interest and angular orientation measurement data of saidfirst image capture device to said second image capture device forguiding angular orientation toward the target of interest based thereon;actuating said second image capture device to capture a second imagewith the target of interest disposed within a field of view thereof;acquiring an angular orientation measurement for each of said first andsecond image capture devices when the first and second images arerespectively captured thereby; executing in a processer a target featurefinder to detect a location of the target of interest within the secondimage by comparatively processing image features of the first and secondimages captured by the first and second image capture devices; andadaptively generating a plurality of user prompts at said second imagecapture device responsive to detection of the location of the target ofinterest in the second image by the target feature finder, the userprompts including: predefined visual indicia to identify the target ofinterest, and orientation correction alerts to guide angular orientationof said second image capture device to situate the target of interestsubstantially centered within the field of view thereof, the orientationcorrection alerts including visually displayed directional markersapplied to the second image, wherein said comparative processing of thefirst and second images by said target feature finder includes:generating a reference Difference of Gaussian (DoG) for at least oneportion of the second image and a target DoG for the target of interest,cross-correlating the reference and target DoG's for a predefined set ofcomputational scale spaces and octaves, summing the cross-correlationsgenerated for each of the computational scale spaces and octaves, anddetermining a maximum value of the summed cross-correlations torepresent the most likely image location for the target of interest. 11.The method as recited in claim 10, further comprising inter-deviceranging to measure a base line distance between said first and secondimage capture devices for parallax angle correction thereat with respectto the target of interest, said inter-device ranging including theexchange of at least one cue signal between said first and second imagecapture devices, said cue signal having a predetermined energy framereference type.
 12. The method as recited in claim 10, furthercomprising actuating each of said first and second image capture devicesfor tracking the target of interest over a series of images subsequentlyacquired thereby, the tracking including, for each subsequently acquiredimage: re-acquiring the angular orientation measurement of said imagecapture device when the subsequent image is acquired; computing adifference between the re-acquired angular orientation measurement andthe angular orientation measurement acquired for the previous imageacquired with the target of interest substantially centered within thedevice field of view; and adaptively generating orientation correctionalerts responsive to the difference computation for guiding angulardisplacement of said image capture device to substantially center thetarget of interest within the field of view thereof.
 13. A system forparallactically synced acquisition of images about a common target frommutually displaced imaging positions, the system comprising: at leastfirst and second imaging devices disposed in displaceable manner atrespective first and second imaging positions, said first imaging deviceacquiring a first image with a target of interest disposed at apredetermined relative position within a field of view thereof, saidsecond imaging device acquiring a second image with the target ofinterest disposed within a field of view thereof; at least oneorientation sensor collectively acquiring an instantaneous angularorientation measurement of the first and second imaging devices whenimages are acquired thereby, the angular orientation measurement of thefirst imaging device transmitted from the first imaging device to thesecond imaging device to thereby guide preliminary angular adjustment ofsaid second image capture device toward the target of interest; a targetfeature finder module detecting a location of the target of interestwithin at least the second image by comparatively processing imagefeatures of the first and second images acquired by the first and secondimaging devices; and an integration module coupled to said targetfeature finder module, said integration module generating a plurality ofuser prompts at said second imaging device responsive to detection ofthe location of the target of interest in the second image by the targetfeature finder module to thereby further guide angular adjustment ofsaid second imaging device based on the comparative processing of theimage features, the user prompts including: visual indicia adaptivelyapplied to the second image to visually distinguish the target ofinterest, and orientation correction alerts adaptively generated toguide angular displacement of said second imaging device to situate thetarget of interest at the predetermined relative position within thefield of view thereof, wherein, when a selected one of the first andsecond imaging devices is actuated to acquire at least one subsequentimage: the at least one orientation sensor acquires a subsequent angularorientation measurement of said selected imaging device relative to theknown reference point when the subsequent image is acquired, theintegration module actuates computation of an orientation differencebetween the subsequent angular orientation measurement and an angularorientation measurement acquired for a previous image acquired by saidselected imaging device, and the integration module adaptively generatessubsequent orientation correction alerts responsive to the orientationdifference computation to thereby guide subsequent angular adjustment ofsaid selected imaging device to situate the target of interest at thepredetermined relative position within the field of view thereof. 14.The system as recited in claim 13, wherein said first and second imagingdevices each include an orientation sensor, each said orientation sensorincluding inertial measurement unit acquiring an angular orientationmeasurement therefor when the first and second images are respectivelyacquired thereby.
 15. The system as recited in claim 14, wherein: saidfirst imaging device transmits target of interest data to said secondimaging device, said second imaging device being guided to slew inangular orientation toward the target of interest based on thetransmitted target of interest data and transmitted instantaneousangular orientation measurement, the predetermined relative position forthe target of interest being centered within the field of view of eachsaid imaging device; and said first and second imaging devices areactuated to exchange at least one cue signal therebetween forinter-device ranging, the system actuating parallax angle correction forat least one of said first and second imaging devices with respect tothe target of interest, said cue signal having a predetermined energyframe reference type.
 16. A system for parallactically syncedacquisition of images about a common target from mutually displacedimaging positions, the system comprising: at least first and secondimaging devices disposed in displaceable manner at respective first andsecond imaging positions, said first imaging device acquiring a firstimage with a target of interest disposed at a predetermined relativeposition within a field of view thereof, said second imaging deviceacquiring a second image with the target of interest disposed within afield of view thereof; a target feature finder module detecting alocation of the target of interest within at least the second image bycomparatively processing image features of the first and second imagesacquired by the first and second imaging devices; and an integrationmodule coupled to said target feature finder module, said integrationmodule generating a plurality of user prompts at said second imagingdevice responsive to detection of the location of the target of interestin the second image by the target feature finder module, the userprompts including: visual indicia adaptively applied to the second imageto visually distinguish the target of interest, and orientationcorrection alerts adaptively generated to guide angular displacement ofsaid second imaging device to situate the target of interest at thepredetermined relative position within the field of view thereof,wherein said comparative processing of the first and second images bysaid target feature finder module includes: generating a referenceDifference of Gaussian (DoG) for at least one portion of the secondimage and a target DoG for the target of interest, cross-correlating thereference and target DoG's for a predefined set of computational scalespaces and octaves, summing the cross-correlations generated for each ofthe computational scale spaces and octaves, and determining a maximumvalue of the summed cross-correlations to represent the most likelyimage location for the target of interest.